1. Land, Air, and Water
Chapter 2, Section 2

2. Forces Inside the Earth
About 90% of the world’s earthquakes and many of the world’s active volcanoes occur in the Ring of Fire which circles the Pacific Ocean
Earthquakes and volcanoes are two forces that shape and reshape the Earth.
Provide clues about the Earth’s structure

4. What is the Earth Made of?
Water covers 75% of Earth’s surface in lakes, rivers, seas, and oceans
Only 25% of Earth’s surface is land
Continents are unique because of their landforms, or shapes and types of land
Mountains are landforms that rise usually more than 2,000 feet above sea level.
Wide at the bottom and rise steeply to a narrow peak

5. What is the Earth Made of?
Hills are lower and less steep than mountains, with rounded tops
A plateau is a large, mostly flat area that rises above the surrounding land
Plains are large areas of flat or gently rolling land

6. Pangaea: The Supercontinent
Geographers theorize that millions of years ago the Earth had only one huge landmass. They called it Pangaea.
Scientists reasoned that 200 million years ago, a force made Pangaea split into several pieces and it began to move apart. Separate pieces formed continents.

8. Pangaea: The Supercontinent
Geographers explained the separation of the continents with plate tectonics
The outer skin of the Earth, called the crust, broke into huge pieces called plates
Continents and oceans = top of crust
Magma, layer of hot rock = below plates
Plates float on the magma
Continents are part of plates that shift over time

10. Volcanoes, Earthquakes, and Shifting Plates
Plates move in different directions
Plates move apart and magma leaks out through cracks in the crust
In the oceans the cooling rock forms underwater mountains (ridges)
Plates push against each other forcing one plate under another
Volcano is produced when pressure and heat build up

11. Volcanoes, Earthquakes, and Shifting Plates
Weak places along plate boundaries
Crust cracks and splinters from the pressure (faults)
Earthquake  crust moves along fault lines and releases great amounts of energy

13. Forces on the Earth’s Surface
Forces either build up the Earth or break it down
Weathering  process that breaks rocks down into tiny pieces
Wind, rain, ice
Helps create soil
Erosion  small pieces of rock carried to new places

15. Air and Water: Two Ingredients for Life
Atmosphere  a thick layer of gases that surrounds the Earth
Provides oxygen for people and animals
Provides carbon dioxide for plants
Holds in heat from the sun

16. Air and Water: Two Ingredients for Life
About 97% of the Earth’s water is found in oceans
Fresh water makes up a small %
Most is frozen in the North and South poles
Lakes, rivers, rain, groundwater